PR rotory valve

[niesenracing]

Could someone tell me how to time the rotory valve. Had to take a part
because of piston ring failure.

[russhill]

Just set engine on top dead center (pistons all the way up). Hold valve so you can look straight through it. Bolt it on--all 5 bolts.

In the old days, there were therorists who could explain in detail why it should be advanced or retarded one tooth or even two teeth. But we beat them.

Russ Hill

[niesenracing]

Thanks for your information I thought when I took it a part it was striaght.

[David Everhart]

Get a degree wheel from someone or buy one from summitt racing for 14.00. Then set it on top dead center. Valve should just close when the motor is advanced to 70 degrees after top dead center. This has to do with the intake port timing and whether or not the motor blows fuel back into the boat from the rotor being open at the wrong time. A good book to read or get is the Carpenter manual about PR's
David Everhart S52

[russhill]

Straight through at top dead center is as good as it gets. On the old factory rotary valves there was a cap screw which when open you could see the edge of the gear and on the gear was a J (for Johnson). It was supposed to be visible at so many degrees before or after something.

Going by opening or closing is fallacious, because by now, there isn't a stock rotary valve core in the world. They've all been cut and filed and futzed with so that probably both sided don't even close at the same degree.

There is some truth to the fact if the back of your life jacket is always wet and oily, the valve is too far advanced--back off one tooth. You will not be able to detect any difference in performance.

I remember a discussion with the great Bill Tenney once at Salton Sea about rotary valves. He said he had tried advancing, retarding etc until the engines wouldn't even run. I was gaga and said, yeah, yeah --what'd you find out? He said it doesn't matter where you set them. We found the same thing at Hubbell's on his dyno.

Russ Hill

[RichardKCMo]

There is some truth to the fact if the back of your life jacket is always wet and oily, the valve is too far advanced.

Leave it to the Hills, another little tidbit........ thanks Russ.
RichardKCMo